Corrosion inhibited phosphoric acid composition

ABSTRACT

A CORROSION INHIBITED PHOPHORIC ACID COMPOSITION COMPRISING A PHOSPHORIC ACID SOLUTION HAVING ADDED THERETO AN EFFECTIVE AMOUNT OF THE REACTION PRODUCT OF AN ACIDIC FLUORIDE WITH AN ORGANIC AMINE HAVING A MOLECULAR WEIGHT BETWEEN ABOUT 50 AND ABOUT 500.

United States Patent CORROSION INHIB TED PHOSPHORIC ACID COMPOSITION Olen L. Riggs, Jr., and David W. Barnett, Ponca City, Okla, assignors to Continental Oil Company, Ponca City, Okla. No Drawing. Filed Feb. 9, 1968, Ser. No. 704,251

Int. Cl. C23f 11/00 US. Cl. 252--389 4 Claims ABSTRACT OF THE DISCLOSURE A corrosion inhibited phophoric acid composition comprising a phosphoric acid solution having added thereto an eflective amount of the reaction product of an acidic fluoride with an organic amine having a molecular weight between about 50 and about 500.

This invention relates to novel and useful compositions and methods for inhibiting the corrosion of metals by phosphoric acid.

At the present time metals are protected from phosphoric acid corrosion by rubber linings and by the addition of certain inhibitors to the phosphoric acid.

It has now been unexpectedly discovered that the corrosivity of metal surfaces in contact with phosphoric acid can be markedly reduced by adding to said acid an effective amount of the material obtained by reacting an acidic fluoride with an organic amine having a molecular weight between about 50 and about 500.

The preferred organic amines which can be reacted with an acidic fluoride to produce the desired reaction product are essentially all aliphaticalkyl mono or diamines, imidazolines, guanidines, ethoxylated monoamines and ethoxylated diamines. Some specific examples are shown by the following structural formulas:

RCH2 H-CH; R=4 to 11 carbons 2. R-NHz R=18 to 22 carbons R1 ICH;CH2CH2NHz R=12 to 16 carbons 4. (CHzCHzOhH (CH2CH20) H R=11 to 17 carbons 5. NCH2 R--N-llh H2CH2NH2 R=11 to 17 carbons 6. (CHzCH20) 1H (CH2CH2O) 1H RNCH2CH2CH2N (CH2CHzO) H R= to 16 carbons R-(i-CH;

HNCHZCHZCHZNHZ R=1O to 16 carbons Hydrogen fluoride is the preferred acidic fluoride; however, other acidic fluorides such as H SiF can also be used.

The mole ratio of amine to acidic fluoride can vary from about 1:3 to about 3:1, with the preferred ratio being 1:1.

The concentration of reaction product effective to give the desired results can vary from about 100 to about 1000 parts per million with the upper limit being more of an economic limit than a limit on the corrosive effect produced.

3,578,607 Patented May 11, 1971 ice The reaction between the organic amine and the acidic fluoride is preferably carried out in the presence of isopropanol and at reflux conditions at about C. The amount of alcohol present is not critical but is preferred to be in a quantity which will give the desired concentration of reaction product for addition to the phosphoric acid.

Example 1 shows a procedure which provides the desired reaction product.

EXAMPLE 1 One mole of an organic amine having the structural formula H R-JJ-CHa H-NCH2CH2CH2NH2 R=14 carbons was weighed into a three-necked round bottom flask. One hundred fifty grams of isopropanol and one mole of acidic fluoride were added. The flask Was then heated to 80 C. and allowed to reflux for 3 hours. The entire reaction product was then tested as a corrosion inhibitor for phophoric acid. The results are shown in Example 2.

EXAMPLE 2 Corrosion tests were made using the reaction product of Example 1. The tests consisted of pouring 300 ml. volumes of 75 percent by weight of H P0' into cells containing specimens of annealed 1020 carbon steel. The results are given in Table 1.

TABLE 1 [75% wt. HaPOi, 24 0., 2 hrs.]

Reaction product 25% active concentration, Wt. loss, Percent p.p.m. g. protection 0 0. 20290 HF 0. 14035 30. 8 200 0. 09955 50. 9 500 0. 06410 6. 84 1, 000 0. 05605 72. 3 100 0. 16845 16. 9 HzSiFu 200 0. 13530 33. 3 500 0. 10340 49. 0 1, 000 0. 05745 71. 6

Table 2 illustrates that the beneficial effect does not occur when the amines and hydrogen fluoride are present as an unreacted simple mixture.

TABLE 2 [75% Wt. HaPOi, 24 0., 2 hrs.]

Wt.loss,

Sample (unreacted) g.

Amine of Example 1 500 p.p.m., 340 21,200 m.p.y., 15% protec- HF 500 ppm. 11. Uninhibited 400 2, 600 m.p.y.

Corrosion ing a structural formula selected from the group consisting of:

RCHz( ]H-CH3 R=4 to 11 carbons 2. R-NHz R=18 to 22 carbons RI ICH2CH2CH2NII2 R=12 to 16 carbons HNCHzCHzCHzNHz R= to 16 carbons where R is an alkyl group and with said organic amine having a molecular weight between about 50 and about 500 and wherein said reaction is carried out under reflux conditions at about 80 C. for about 3 hours in the presence of isopropanol and the ratio of said acidic fluoride to said organic amine is from about 1:3 to about 3:1.

2. The composition of claim 1 wherein the organic amine has the following structural formula:

R-CHz-H-CHa R=4 to 11 carbons 2. R-NHz R= 18 to 22 carbons R-AI-CHzCHzCHzNHz R=12 to 16 carbons R ('3 C Ha HNCHZCHZCHZNI'IQ R=10 to 16 carbons where R is an alkyl group and with said organic amine having a molecular weight between about and about 500 and wherein said reaction is carried out under reflux conditions at about C. for about 3 hours in the presence of isopropanol and the ratio of said acidic fluoride to said organic amine is from about 1:3 to about 3: 1.

4. The method of claim 3 wherein the Organic amine has the following structural formula:

H R--CH:

H-N-CHz-CHz-CHzNHz where R=10 to 16 carbons.

References Cited UNITED STATES PATENTS 2,146,356 2/1939 Schrader et al. 260-583X 3,134,815 5/1964 Burkert et a1. 260583 3,152,160 10/1964 Harrison 260583 3,260,673 7/1966 Fisher 252--148X 3,371,118 2/1968 Lundeen et a1. 260-583 HERBERT B. GUYNN, Primary Examiner A. I. RADY, Assistant Examiner US. Cl. X.R. 

